1. Field of the Invention
The invention relates to an automatic valve, in particular for gas compressors, having at least one sealing member which is essentially designed in the form of a mushroom-shaped piston and which is guided by a guide attachment relative to a catcher plate in the stroke direction and is pre-stressed with a closure head by means of a spring against an opening sealed off in the opposite seating plate.
2. The Prior Art
Valves of this type are also referred to as poppet valves and are known for example from U.S. Pat. No. 2,624,587. With a suitable valve stroke, the individual valves or individual sealing members arranged in groups allow a satisfactory level of efficiency and a long service life as well as a simple stocking of spare parts, maintenance and assembly. The individual sealing members are suspended and guided and have the closure force introduced into them by way of bores in the catcher plate. Designs of this type have been found successful particularly in the case of slowly running reciprocating-piston compressors with a low compression ratio, since it is only in this class of compressor that it is possible in a simple manner to effect the large valve stroke which is necessary for this type of valve and which ensures a high level of efficiency. Problems have arisen in particular in the case of rapidly running compressors since the service life of the individual sealing members is adversely affected by the high opening and closing speeds.
Because of the lower manufacturing costsxe2x80x94as compared with annular or plate valvesxe2x80x94also because of the simplified stocking of spare long time to use poppet valves of this type in other classes of compressors as well, in which case, however, difficulties have always arisen with the large valve strokes required for an efficiently operating valve of this type or the high opening and closing speeds associated therewith. In addition, because of the guide length of the sealing members required in the length of stroke the catcher plate has to be made very thick, and this results in an undesired increase in the manufacturing costs, in particular of the catcher plate which in terms of mechanical stressing would need only a fraction of the thickness required for receiving, guiding and springing the sealing members.
The problems mentioned are solved in part in an arrangement known for example from U.S. Pat. No. 4,489,752 in that a central guide pin for the closure member is inserted in the catcher plate, as a result of which the guide length of the sealing member is independent of the thickness of the catcher plate. The reliable fastening of this guide pin in the catcher, however, requires an increased level of care in production and assembly.
The object of the present invention is to improve a valve design of the type defined in the introduction, in such a way that the above-mentioned drawbacks of the known designs described are avoided and that, in particular, a simple and inexpensive design, manufacture and assembly, as well as use in fields of application previously closed to valves of this type are made possible.
This is attained according to the present invention in the case of a valve of the type defined in the introduction in that the guide attachment of the or each sealing member together with the spring is arranged and supported in a cup-like suspension member inserted in a continuous receiving bore in the catcher plate and is guided with its external periphery at least in part directly on the internal periphery of the suspension member. In this way, an individual cup-like suspension member with a guide length of any desired size can be inserted and also fastened in a supported manner in a thinxe2x80x94as compared with the length of stroke of the sealing membersxe2x80x94catcher plate per individual sealing member in a simple manner, and this makes possible a light, material-saving design. In this way, guided lengths of strokexe2x80x94of any desired size within wide boundariesxe2x80x94of the sealing members can be produced in a simple and advantageous manner, the modular design ensuring a simple assembly and maintenance as well as stocking of spare parts.
In accordance with a particularly preferred embodiment of the invention, it is provided that, in order to limit the stroke of the sealing member, the guide attachment thereof cooperates at its end remote from the closure head with a stop on the base of the suspension member. In this way, an impactxe2x80x94resilient to a certain degreexe2x80x94of the opening closure member upon the catcher occurs over the length of the cup-like suspension member between its retention in the catcher plate and the atop, and this reduces the stressing of the components and contributes to an increase in the service life, and particularly of course in the case of suspension members of plastics material or similarly resilient materials.
In a preferred embodiment of the invention the suspension member can be inserted into the catcher plate from the side of the seating plate and can be fixed thereon by means of a fastening member preferably constructed in the form of a snap or screw design. On the one hand this ensures that even if the fastening becomes loose, the cup-like suspension member cannot fall out of the catcher plate and lead to operating failures, whilst, on the other hand, a simple possibility of replacement is still retained.
In an additionally preferred embodiment of the invention the suspension member and/or the sealing member can consist of plastics material not susceptible to impact, preferably glass- or carbon-fibre-reinforced PA (polyamides), PEEK (polyetheretherketone), PPS (polypheneline sulphide) or part-aromatic PA (polyamides), optionally with additives which improve the sliding properties, such as in particular MoS2, PTFE (polytetrafluoroethylene) PFA (polyfluoroalkoxy) or graphite and can preferably be produced in the injection-moulding process. This makes possible robust and inexpensive designs of the wearing parts and thus opens up further cases of application.
In accordance with a particularly preferred further embodiment of the invention, the spring pre-stressing the sealing member can be constructed in one piece with the suspension member or the sealing member, and this allows a prevention of rotation to reduce problems of wear as well as a reduction of assembly costs in a simple manner.
The invention will be explained in greater detail below with reference to the embodiments illustrated diagrammatically in the drawings.